An information recording/reproducing unit has so far been employing such a recording medium control system as described typically in the standards ISO10089, ISO10090 and ISO10091 for use with a magneto-optic disk, for example, whereby the recording area of a recording medium is broadly divided into three areas (user area, alternate area and data medium control area).
A user area is used for recording/reproducing the data required by higher level units. An alternate area is used as an alternate sector for alternate processing, wherein data are recorded, by substituting a defective sector in the user area. A data medium control area is used for recording/reproducing a defective list and alternate list to control the alternate processing.
When data is recorded in a user area of a recording medium, a determination is made on whether recording errors are generated or not, or whether data is correctly recorded or not, by a method of comparing signals obtained by reproducing immediately after recording the data with the data that was intended for recording, and the like for each respective sector, for example.
In general, recording errors are generated due to partial defects of a recording medium itself and a malfunction in the record system of a recording/reproducing unit.
When recording errors are found to have been generated, the previous data is again recorded in an alternate sector within an alternate area by substituting the defective sector of the user area wherein recording of data was made before, and at the same time defects control information that provides positional information on the defective sector and alternate sector is recorded in the data medium control information area.
How these user area, alternate area and data medium control information area are structured can be determined arbitrarily. For example, a track of data medium on the disk of an information recording/reproducing unit as shown in FIG. 15 is defined as one of a plurality of paths formed on the data medium by the division thereof performed along the radius of the disk and each respective track of the above is divided along the direction of rotation into 16 segments, each being called a sector.
Assuming there are a data medium control information area, user data area and alternate area on the foregoing data medium, for example, FIG. 12 shows how a structure is formed on the record medium.
Here, 601 indicates a first data medium control information area, 602 indicates a second data medium control information area, 603 indicates a user area, 604 indicates an alternate area, 605 indicates a third data medium control information area and 606 indicates a fourth data medium control information area. The data medium control information is formed of the user area 603 detected at the time of initialization of a recording medium 600, primary defect lists (PDLs) 608a and 608b that keep the positional information on an alternate sector in the alternate area 604, secondary defect lists (SDLs) 609a and 609b that indicate a defective sector detected at the time of data recording in the user area and the positional information on an alternate sector in the alternate area with data recorded by substituting the defective sector, and a disk definition structure (DDS) 607 that indicates the start of data medium control information, fixed start addresses of PDLs 608a and 608b and SDLs 609a and 609b and a data structure on the record medium (positional information on ROM data, RAM data and the like).
In other words, the data medium control information comprises DDS607, PDL608a and 608b, and SDL609a and 609b, and the similar data are recorded in each respective data medium control information area.
A RAM612 is a memory wherein reproduced data medium control information is stored. The description that follows employs SDL609a and 609b whereby data medium control information is updated when a defective sector is found.
The present example of prior art adopts a 2 sector state for both PDL and SDL.
When a recording medium 600 is loaded in a recording/reproducing unit for execution of data recording/reproducing, DDS607, PDL608a and 608b, and SDL609a and 609b are reproduced and then stored in a RAM612.
When data medium control information is changed, the SDL stored in the RAM 612 is recorded in each of the first to fourth data medium control information areas 601, 602, 605 and 606 on the recording medium, respectively. Accordingly, every time when a defective sector in the user area is detected, positional information on the defective sector, an alternate sector replacing the defective sector and the like is added to the RAM612, thereby updating the SDL in the RAM612.
The SDL after the foregoing updating is recorded in each of the first to fourth data medium control information areas 601, 602, 605 and 606 on the recording medium, respectively.
The SDL stored in the RAM612 is recorded in each of the first to fourth data medium control information areas 601, 602, 605 and 606 on the recording medium 600, respectively.
An example of the contents of these SDL809a and 809b is shown in FIG. 14(a), wherein the data unit of SDL is 1 byte, the reference numeral 800 shows a defect list identifier formed of 2 byte fixed data, the reference numeral 801 shows a reserved field held for future expansion, the reference numeral 802 shows the number of defective sectors held in the SDL, the reference numeral 803 is the address to show a location of a defective sector, the reference numeral 804 is the address to show a location of an alternate sector substituting the foregoing defective sector, and the reference 805 shows a blank field set aside for defective sectors that are detected in future.
Here, each respective positional information on a pair of defective sector and alternate sector is expressed by employing the data 803 and 804 formed of 8 bytes.
According to this SDL, it is understood that the number of defect cataloged is 1, the address (X1) is a defective sector and the address (Y1) is an alternate sector replacing the foregoing defective sector.
Thus, an inability to use data medium control information due to partial defects on a recording medium and the like has been prevented in the prior art by recording data medium control information in a plurality of data medium control information areas. However, when the data medium control information in RAM612 is recorded on a recording medium 600, the data of the RAM612 are sometimes not updated correctly because of partial defects on the recording medium.
At this time, the data medium control information area is not allowed to read-in, resulting in a reduction of usable data medium control information areas by one.
Therefore, if there are any defective sectors, even only one, in the data medium control information area, the use of the data medium control information area becomes impossible.
More specifically, a problem was encountered in the past that the entire data medium could not be used due to the existence of 4 defective sectors.
With the alternate list and defect list in the prior art, recording locations are fixed as shown in FIG. 12 and assuming that the number of byte for 1 sector is 512 bytes and defective and alternate sectors as many as 63 are cataloged in SDL, for example, this SDL becomes 512 bytes, resulting in using up exactly 1 sector.
Further, when an address (X2) to be used as the next SDL happens to be a defective sector, a sector on a certain user area is a defective sector. Assuming that recording is executed on that sector which is a defective sector, a recording error is caused, thereby generating an alternate sector with new addresses of defective sector and alternate sector cataloged in the SDL. As a result, the cataloged number becomes 64 and the number of byte used counts 520 bytes, exceeding the number of byte for 1 sector with a resulting addition of 1 sector to the SDL. This added SDL sector is recorded on a defective sector, resulting in an inability to use this SDL.
Thus, the inability to use an SDL that has been usable till halfway happened all over the data medium control information area, resulting in a problem of not allowing recording or reproducing to be performed in any areas of the entire data medium.